While the 55 mile-per-hour speed limit has been credited with reducing fatality rates on modern highways, drivers who use older roads have not reaped similar safety benefits, according to the Road Information program.

In 1974, the first year of the nationwide reduced speed limit, fatality rates on the interstae highway system in Virginia dropped 34.2 per cent, and increased 3.5 per cent on locl roads and streets, a road information program spokesman said. Nationally, fatality rates on the interstae highway system dropped 32.6 per cent, compared with a decrease of only 1.6 per cent on local roads and streets. Rates have remained in proportion since then, the spokesman said.

One National Highway Traffic Safety Administration study on the safety benefits of reduced speed limits found "the high speed highway systems experiencing large savings and the local type rural roads showing no improvements."

The American Association of state Highway Transportation Officials studied the 55 m.p.h speed limit and concluded that "roads with the highest design standards have the lowest accident ad fatality rates," the spokesman said.

Howard L. Anderson associate administrator for safety at the Federal Highway Administration, points to the interstae system as "probably the most outstanding example of the impact of good roadway design on highway safety." He credits the system with saving 60,000 lives since 1956, when the first miles were opened.

But even when complete, the Road Information program reports, the proposed 42.500-mile interstate system will comprise only 2.3 per cent of the total 1.8 million miles of paved roads in the nation. Of that total, it reports, 800,000 miles have problems which can affect safe driving. Bumps, ruts, potholes, broken pavement, shoulder drop-offs, blind curves, narrow lanes, steep hills and obsolete bridges are among the most common hazards, they warn.

Giving to much credit to the 55 mile-per-hour speed limit may lull some drivers into thinking they can be less careful on local, low-speed roads when just the opposite is true, said H.W. Reece, president of the Road Information program, a transportation industry-sponsored study agency. "it may also tempt some drivers to speed on back roads where they think laws are not enforced," he said.